How much sodium silicate to get 2ppm in 200mL?

[Miami Reef]

I want to make an experiment to see if sodium silicate will cause a phosphate false reading with the Hanna PO4 ULR.

@taricha tested with the Hanna Phosphorous ULR, and someone said that although the phosphorous checker doesn’t have much of an interference, the Phosphate Checker does.

I will make 200mL of saltwater in a glass beaker with my magnetic stirrer.

I will test phosphates and silicate prior in the Red Sea Blue seawater mix.

Most likely the starting phosphate will be at 0.00ppm.

I will then spike the silicate to 2ppm, and test the phosphate to see if there is a rise. I will not dose phosphates at all. Let me know if I should to make the experiment more accurate.

This is the sodium silicate I will be using:

 

[Randy Holmes-Farley]

You measuring it by a scale or a pipette?

 

[Miami Reef]

You measuring it by a scale or a pipette?

Scale. I have a 0.0001g scale.

 

[taricha]

Click through this quote for details, I talked Rick into checking the SiO2 interference on PO4 packets for the 3 different hanna packets commonly used: ULR P, ULR PO4, and LR PO4 packets.

what we got was basically 100 to 1. That is, say 20 ppm SiO2 could give +0.20ppm PO4. (so significant interference in PO4 seems to require very large amounts of SiO2.)

This might be what you are proposing to check or replicate @Miami Reef

Right. Here's what Rick and I measured in 2020, it takes a whole lot of Si to make the hanna PO4 read too high to a degree that anyone should care about.


But for some reason it keep coming up where people seem to think that a ppm or two of Silica makes Hanna PO4 tests unusable, so after I rechecked again this year (and got same basic results) I asked @Rick Mathew to take another look with multiple different hanna PO4 packets: ULR P, ULR PO4, LR PO4.
None of them looks much different than what we saw in quoted post above.

You can see that the three different hanna packets all give roughly similar result. For ballpark purposes, call it 100:1. For each 0.01ppm PO4 interference, you need about 1ppm SiO2 to generate it.

Some people seemed to think that Si was causing and extra +0.5ppm PO4 or higher, so Rick even ran up the SiO2 to see just how high you had to go to get something like that....

The 100 to 1 seems still a decent ballpark picture, you need somewhere around ~50ppm SiO2 to get +0.5ppm PO4 reading.

 

[Randy Holmes-Farley]

OK, so we will assume from the bottle label that it is 41% Na2SIO2 and the goal is to make 2 ppm SiO2.

Na2SIO2 has a mw of 106 and the SiO2 has a mw of 60, so that 41% is 60/106 x 100 = 56.6%.

Thus the product is 23.2% SiO2 by weight.

To make 2 ppm SiO2 we want 2 mg/L SiO2, or0.4 mg/200 mL.

Thus, we want to add 0.4 mg/.232 = 1.7 mg of the product to 200 ml of water.

 

[Miami Reef]

Click through this quote for details, I talked Rick into checking the SiO2 interference on PO4 packets for the 3 different hanna packets commonly used: ULR P, ULR PO4, and LR PO4 packets.

what we got was basically 100 to 1. That is, say 20 ppm SiO2 could give +0.20ppm PO4. (so significant interference in PO4 seems to require very large amounts of SiO2.)

This might be what you are proposing to check or replicate @Miami Reef

Thank you, Taricha. I didn’t know you tested all 3 reagents.

So it’s settled: Silica within normal ranges (about 2ppm) does not cause a significant increase of phosphate.

That’s what I was saying. Thank you.

 

[Miami Reef]

OK, so we will assume from the bottle label that it is 41% Na2SIO2 and the goal is to make 2 ppm SiO2.

Na2SIO2 has a mw of 106 and the SiO2 has a mw of 60, so that 41% is 60/106 x 100 = 56.6%.

Thus the product is 23.2% SiO2 by weight.

To make 2 ppm SiO2 we want 2 mg/L SiO2, or0.4 mg/200 mL.

Thus, we want to add 0.4 mg/.232 = 1.7 mg of the product to 200 ml of water.

Thank you so much for the math, Randy.

I am not going to do the test because Taricha already did it. I really appreciate you showing the math. I will still learn it, and I can always use it for the future if I want to dose silica in different sized tanks. Thank you.

Bookmarked.

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.

 

[taricha]

Thank you so much for the math, Randy.

I am not going to do the test because Taricha already did it.

Nothing wrong with replicating.
If you've got the stuff to do it already, and are confident in making known concentration solutions, then I'd be interested in seeing it checked by someone other than me and Rick.
Or if you don't want to bother, fine either way.

 

[Miami Reef]

edit

 

[Reefahholic]

0.1mL per 15 gallons = 1ppm Si.

You can convert from there.

 

[Miami Reef]

Forget it. I tried doing the experiment, but I saw a lot of inconsistencies with the checkers.

I tested Silica right after dosing: 0.80ppm.

The next morning: 1.80ppm.

Phosphates did appear to rise after dosing Si.

Last night it was 0.11, this morning it was 0.08ppm (started at 0.03ppm)

Let’s just pretend this thread never existed.

 

[gbroadbridge]

OK, so we will assume from the bottle label that it is 41% Na2SIO2 and the goal is to make 2 ppm SiO2.

Na2SIO2 has a mw of 106 and the SiO2 has a mw of 60, so that 41% is 60/106 x 100 = 56.6%.

Thus the product is 23.2% SiO2 by weight.

To make 2 ppm SiO2 we want 2 mg/L SiO2, or0.4 mg/200 mL.

Thus, we want to add 0.4 mg/.232 = 1.7 mg of the product to 200 ml of water.

Just reviving the dead thread

Using a very similar strength product, would someone mind calculating how much would be required to raise 100l by 1ppm.

I have either a faulty test kit or a faulty brain because I'm not getting the results I'm expecting using a Salifert test kit.

 

[taricha]

I have either a faulty test kit or a faulty brain because I'm not getting the results I'm expecting using a Salifert test kit.

salifert Si test fails for most people who try it. Gives zero or near zero even on known Si stock solutions.

 

[gbroadbridge]

salifert Si test fails for most people who try it. Gives zero or near zero even on known Si stock solutions.

Thanks, I haven't used the Salifert test kit before.

Alternative seems to be the Hanna LR Silica but this is a one off experiment and I don't really want to spend $120 on a test kit.

I've dosed 0.5ml/100l which I think should be around 2ppm, but the test is simply showing zero.

 

[taricha]

Alternative seems to be the Hanna LR Silica but this is a one off experiment and I don't really want to spend $120 on a test kit.

I've dosed 0.5ml/100l which I think should be around 2ppm, but the test is simply showing zero.

You could try the seachem Silicate kit. It's cheap and I haven't seen much on it, and if you are aiming for ~1-2ppm, it might be fine for that purpose.
If you do, let us know how it works.

 

[gbroadbridge]

You could try the seachem Silicate kit. It's cheap and I haven't seen much on it, and if you are aiming for ~1-2ppm, it might be fine for that purpose.
If you do, let us know how it works.

Thanks, there is actually one available at a local shop for about $32 so I may try it.

But if someone would be so kind as the check my dosing calculation first, as perhaps the Salifert is correct and I am not dosing enough.

 

[Miami Reef]

Just reviving the dead thread

Using a very similar strength product, would someone mind calculating how much would be required to raise 100l by 1ppm.

I have either a faulty test kit or a faulty brain because I'm not getting the results I'm expecting using a Salifert test kit.

425mg or 0.43g for 1ppm Si.

 

[gbroadbridge]

425mg or 0.43g for 1ppm Si.

Hmmm.

Well I'm up to 3 times that so I think perhaps I should stop
Salifert is still testing zero.

That's unfortunate, as the other salifert tests are pretty good.

 

[taricha]

Well I'm up to 3 times that so I think perhaps I should stop
Salifert is still testing zero.

Yeah, seen about a dozen users try the salifert kit on water with known Si addition and only like 1 reported it worked.
Was total zero for me as well.